Cardiorespiratory consequences to hobble restraint.

UNLABELLED: Mechanical restraints in agitated, violent psychiatric patients are still sometimes in use in the initial phase of emergency treatment, especially when patients are taken to hospital by law enforcement. Sudden death has occurred in persons in hobble restraint. Cardiopulmonary response to prone or upright hobble restraint for three minutes was investigated in six male volunteers in randomised crossover trial. RESULTS: No change was observed in the investigated cardiopulmonary parameters after hobble restraint in the upright position. After hobble restraint in the prone position, mean forced vital capacity decreased by 39.6%, mean forced exspiratory volume by 41%, mean end-tidal carbon dioxide increased by 14.7%, mean heart rate decreased by 21.3%, mean systolic blood pressure decreased by 32.3%, mean diastolic blood pressure decreased by 26.1% and mean cardiac output decreased by 37.4% (P for all reported changes < 0.01). CONCLUSION: Hobble restraint in the prone position leads to a dramatic impairment of hemodynamics and respiration. Upright position and frequent control of vital parameters are necessary to prevent a possibly fatal outcome in persons in hobble restraint.

Cardiorespiratory response to free suspension simulating the situation between fall and rescue in a rock climbing accident.

Many factors contribute to the risk of late death after successful rescue in a rock climbing accident. One factor may be hemodynamic and respiratory compromise by free suspension in a rope between fall and rescue. The risk probably results from using a chest harness alone or the combination of a chest harness and a sit harness. No trials on the acute cardiorespiratory response to free suspension in rock climbing have been reported so far. The effect of 3 min free suspension in a chest harness or in a sit harness on cardiopulmonary parameters was investigated in a randomized, cross-over trial in six healthy volunteers in a simulated rock climbing accident. Measurements were performed before and during the suspension at an altitude of 171 m. No statistical change in cardiopulmonary parameters was observed after free suspension in the sit harness. After free suspension in the chest harness, mean forced vital capacity decreased by 34.3% and mean forced expiratory volume decreased by 30.6%. No statistical change of arterial oxygen saturation occurred and mean end-tidal carbon dioxide increased by 11.5%. Mean heart rate decreased by 11.7%, mean systolic blood pressure decreased by 27.6%, mean diastolic blood pressure decreased by 13.1%, and mean cardiac output decreased by 36.4%. The p value for all reported changes was <0.05. We conclude that free suspension in a chest harness leads to a dramatic impairment of hemodynamics and respiration. This may contribute to the risk of a fatal outcome if rescue is not timely.

How can acute mountain sickness be quantified at moderate altitude?

Reports of acute mountain sickness (AMS) at moderate altitude show a wide variability, possibly because of different investigation methods. The aim of our study was to investigate the impact of investigation methods on AMS incidence. Hackett's established AMS score (a structured interview and physical examination), the new Lake Louise AMS score (a self-reported questionnaire) and oxygen saturation were determined in 99 alpinists after ascent to 2.94 km altitude. AMS incidence was 8% in Hackett's AMS score and 25% in the Lake Louise AMS score. Oxygen saturation correlated inversely with Hackett's AMS score with no significant correlation with the Lake Louise AMS score. At moderate altitude, the new Lake Louise AMS score overestimates AMS incidence considerably. Hackett's AMS score remains the gold standard for evaluating AMS incidence.

Tracheal rupture after emergency intubation during cardiopulmonary resuscitation.

We describe a case of tracheal rupture following an emergency intubation during cardiopulmonary resuscitation. This complication occurring during resuscitation has not apparently been reported previously. Possible causes during the management of cardiac arrest are discussed with references to previously described cases of tracheal rupture.

Effect of alcohol on body core temperature during cold-water immersion.

This study investigates the influence of alcohol on body core temperature during cold-water immersion in human volunteers. In this randomised, double-blind, placebo-controlled crossover trial, 8 healthy male volunteers were randomised to drink 1 litre of beverage containing 50 g alcohol or placebo before 20 degrees C cold-water immersion for 1 hour. Body core temperature was measured before cooling and after 1 hour of immersion with an infrared ear thermometer. After a 1-week interval subjects crossed to the other study branch. In the placebo test, mean temperature decreased after immersion by 0.66 degrees C; after the alcohol mean temperature decreased by 1.0 degrees C (mean difference 0.34, 95% CI 0.14-0.53, P = 0.002).

Emergency mechanical ventilation at moderate altitude.

Portable emergency ventilators are commonly used in the prehospital setting in the transport of critically ill patients in hypobaric environments. The aim of our trial was to evaluate the influence on minute ventilation and blood gas analysis of moderate altitude (3000 m) compared to 171 m in healthy volunteers during mechanical ventilation with the Draeger Oxylog ventilator. At 3000 m, the delivered minute volume increased by 9.8% in the air mix mode and by 14.6% in the no air mix mode. PaO2 at 3000 m altitude decreased by 33.3% in the air mix mode, and no statistical change was observed in the no air mix mode. PaCO2 at 3000 m altitude decreased by 9.0% in the air mix mode and by 12.8% in the no air mix mode. These changes are of sufficient magnitude and importance to require monitoring of minute volume to prevent barotrauma or volume-related trauma and to monitor oxygenation by pulse oximetry during emergency mechanical ventilation at moderate altitude.

Poor ventilatory response to mild hypoxia may inhibit acclimatization at moderate altitude in elderly patients after carotid surgery.

Peripheral chemoreceptors (carotid bodies) are the main sensing organs for hypoxaemia. During carotid surgery, the carotic body in the bifurcation of the common carotid artery is often involved and damaged or destroyed. Animals lose their ability to adapt to high altitude after experimental denervation of the carotid bodies. The objective of our study was to evaluate the ability of human patients to adapt to moderate altitude after single side carotid surgery. Blood gas analysis at rest at 171 m and after car and cable car transport to 1600 m before and after carotid surgery was performed. Mean(s.d.) paO2 decreased insignificantly from 74.8(3.56) at 171 m altitude to 71.6(2.07) at 1600 m (P = n.s.), means(s.d.) paCO2 decreased significantly from 36.2(2.86) to 31.4(2.7) mmHg (P < 0.05) before carotid surgery. Months after surgery, a significant drop in paO2 occurred after identical passive exposure to moderate altitude: mean(s.d.) paCO2 at 171 m 74.4(3.65) mmHg, at 1600 m 65.8(3.70) mmHg (P < 0.01), paCO2 did not change significantly. Mean(s.d.) paCO2 at 171 m: 36.0(2.35), at 1600 m 36.2(2.86) mmHg (P = n.s.). Although the sample investigated was small, after single side carotid surgery patients seem to lose their ability for satisfactory ventilatory response to acute exposure to moderate altitude. This is of possible alpine medical importance.

Effect of alcohol on acute ventilatory adaptation to mild hypoxia at moderate altitude.

OBJECTIVE: To evaluate the influence of alcohol on acute adaptation to mild hypoxia at moderate altitude. DESIGN: Randomized, double-blind, placebo-controlled crossover trial. SETTING: University clinic and mountaineering resort at altitudes of 171 m and 3000 m, respectively, in the Austrian Alps. PARTICIPANTS: 10 healthy male alpinists, 22 to 24 years of age. INTERVENTION: Single dose of 50 g of alcohol or placebo at altitudes of 171 m and 3000 m. MAIN OUTCOME MEASURES: Arterial oxygen pressure (Pao2) and arterial carbon dioxide pressure (Paco2) before and 1 hour after consumption of alcohol or placebo. RESULTS: At an altitude of 171 m, 50 g of alcohol caused no statistical change in Pao2 and Paco2 (median Pao2, 91.5 compared with 90.5 mm Hg [P = 0.89]; median Paco2, 37.5 compared with 36.0 mm Hg [P = 0.41]). At an altitude of 3000 m, the median Pao2 decreased from 69.0 to 64.0 mm Hg, a median decrease in the paired difference of 4.0 mm Hg (95.1% CI, 1.5 to 6.5 mm Hg; P < 0.01), and the median Paco2 increased from 32.5 to 34.0 mm Hg, a median increase in the paired difference of 3.0 mm Hg (95.1% CI, 2.0 to 4.0 mm Hg; P < 0.01) 1 hour after drinking 50 g of alcohol. Placebo did not influence Pao2 or Paco2 at either altitude. CONCLUSION: Alcohol inhibits the initial stages of adequate acute ventilatory adaptation to mild hypoxia at moderate altitude. Caution in the use of alcoholic beverages at moderate altitude is therefore necessary.